Adsorption of heavy metal onto biomass-derived activated carbon: review

Simultaneous removal of heavy metals and antibiotics from anaerobically digested swine wastewater via functionalized covalent organic frameworks

The removal of heavy metal ions and antibiotics from livestock and poultry wastewater has gained significant attention. Developing dual-functional materials capable of simultaneously removing heavy metal ions and antibiotics from wastewater is a promising strategy. In this study, a functionalization approach was proposed to enhance active sites in covalent organic frameworks (COFs), thereby improving their adsorption performance and maintaining photocatalytic activity. Vinyl-functionalized covalent organic frameworks (COFs-V) were first synthesized in a room-temperature solution. Subsequently, 4-mercaptobenzoic acid was introduced into COFs-V via grafting and chelation to prepare COF@COOH, aiming to modify surface active sites. Fourier transform infrared spectroscopy (FTIR) and in-situ X-ray photoelectron spectroscopy (XPS) confirmed the successful introduction of carboxyl groups into COF@COOH, significantly increasing the number of active sites. The performance and mechanism of COF@COOH in the removal of Cu2+, Zn2+, and tetracycline hydrochloride (TC) from swine wastewater were systematically studied. The results revealed that the adsorption capacities of COF@COOH for Cu2+ and Zn2+ reached 19.27 mg/g and 12.95 mg/g, respectively, which were 58 and 29 times higher than those of the unmodified COFs. Additionally, COF@COOH completely degraded TC within 5 min, with 100% photocatalytic degradation efficiency and an apparent rate constant of 1.13 min-1. After five cycles, the adsorption capacities for Cu2+ and Zn2+ and the degradation efficiency of TC remained nearly unchanged, demonstrating the stability of the composite material. This study provides an effective approach for the simultaneous removal of heavy metal ions and antibiotics from swine wastewater.

Sustainable Conversion of Waste PET into Porous Activated Carbon for Efficient Cu2+ Elimination from Aqueous Solution

Heavy metal pollutants, such as Cu2+, pose significant environmental and health risks due to their toxicity and persistence in water systems. Simultaneously, the increasing accumulation of waste poly(ethylene terephthalate) (PET) bottles represents a growing environmental challenge, contributing to plastic pollution. This study addresses both issues by converting waste PET bottles into porous activated carbon (APC) via pyrolysis, creating an efficient and sustainable adsorbent for Cu2+ removal from aqueous solutions. The APC materials were thoroughly characterized by SEM, BET, and XPS analyses, revealing a highly porous structure and abundant oxygen-containing functional groups, which enhance Cu2+ adsorption. The adsorption process was determined to be spontaneous, with a low activation energy of 7.47 kJ/mol, indicating a favorable and energy-efficient adsorption mechanism. Among the APC samples, APC-800 exhibited the best performance, achieving a Cu2+ removal efficiency of 99.30% and a maximum adsorption capacity of 5.85 mg/g. Recyclability tests confirmed the material's durability, maintaining over 96% efficiency during the first three cycles, with a slight decline in later cycles. This study demonstrates a dual environmental benefit: mitigating plastic waste by repurposing PET bottles and providing an effective solution for heavy metal pollution, aligning with circular economy principles, and promoting sustainability in environmental management.

Ultrasound-assisted synthesis of biomass-derived carbon-supported binary metal oxides for efficient adsorption of heavy metals from wastewater

Heavy metal contamination in water sources remains a critical environmental issue, primarily due to industrial activities, in terms of its continuous contribution to pollution through non-compliance and illegal discharge. This study presents an innovative biochar-supported binary metal oxide composite (nickel oxide (NiO) and cobalt oxide (CoO) nanoparticles) synthesized via ultrasound-assisted techniques for efficient adsorption of Zn(ii) and Cd(ii) ions from wastewater. By utilizing solid residues and leveraging ultrasound technology, this approach aligns with the principles of green chemistry due to utilization of a renewable biomass-based source, enhancing energy efficiency in the synthesis process, and minimizing waste production. Thereby a sustainable and innovative route for material development is explicitly demonstrated. Structural and morphological characterizations confirm the uniform integration of Nickel oxide (NiO) and cobalt oxide (CoO) particles into the biochar matrix, leading to maximum adsorption capacities of 18.9 mg g-1 for Zn(ii) and 10.2 mg g-1 for Cd(ii). The adsorption process follows a chemisorptive monolayer mechanism, as demonstrated by kinetic and isotherm studies, and is thermodynamically confirmed to be endothermic and spontaneous. The material also exhibits excellent reusability over five adsorption-desorption cycles. By integrating sustainable resources with innovative synthesis techniques, this work contributes to advancing wastewater remediation technologies while supporting global sustainability initiatives.

Leveraging machine learning for prediction and optimization of texture properties of sustainable activated carbon derived from waste materials

The increasing demand for sustainable waste management has driven innovation in the production of activated carbon (AC) from waste. AC's textural properties, including its surface area (SA), total pore volume (TPV), and micropore volume (MPV), are critical for applications such as gas purification and wastewater treatment. However, the traditional assessment methods are expensive and complex. This study employed machine learning (ML) models to predict AC's properties and optimize its production process. Random Forest (RF), Decision Tree (DT), Gradient Boosting Regressor (GBR), support vector machines (SVM), and Artificial Neural Networks (ANN) were applied along with key input parameters, including raw material type, particle size, and activation conditions. A genetic algorithm (GA) integrated with the GBR model optimizes the synthesis process. The ML models, particularly RF and GBR, accurately predicted SA with R2 values exceeding 0.96. In contrast, the linear regression models were inadequate, with R2 values below 0.6, emphasizing the non-linear relationship between the inputs and outputs. Sensitivity analysis showed that the activation temperature, ratio of the activating agent to carbon, and particle size significantly affected the AC properties. Optimal properties were achieved under activation temperatures between 800 and 900 °C and activating-agent to the carbon ratio 3.8. This approach provides a scalable solution for enhancing AC production sustainability, while addressing critical waste management challenges.

Development of a Treatment System of Water with Cr (VI) Through Models Using E. crassipes Biomass with Iron Chloride

In the context of critical water quality issues, there is a pressing need for more pragmatic approaches to water research. Adsorbent biomass, derived from abundant and effective natural sources, holds considerable promise as a solution. E. crassipes, a type of plant biomass, has emerged as a particularly promising material due to its high adsorption capacity. When combined with iron chloride, this capacity is significantly enhanced, and the addition of EDTA is essential for the reuse of treated water. The economic viability of this material in water treatment has been thoroughly evaluated, and the project was developed with the aim of building treatment systems using E. crassipes biomass in conjunction with iron chloride. The development process involved the creation of a special material composed of 85% dried and ground E. crassipes and 15% iron chloride. The process was scaled up with the most effective biomass for treatment and subsequent elutions with EDTA. The outlet conditions, the quantity of pollutant removed, and the treated volume were established, and subsequently the extraparticle diffusion constant Kf, the intraparticle diffusion constant, and the characteristic isotherm were determined. The identification of the intraparticle diffusion model, Ks, was made possible by the results of the model, which indicated the specific route for the construction of a pilot-scale treatment system. The pilot-scale prototype was constructed using 1000 g of EC (2) of biomass (850 g of E. crassipes and 150 g of chloride of iron). The prototype developed in the present investigation could be used to treat effluents contaminated with heavy metals, especially chromium, and is an advanced environmental research project that contributes to the improvement of water quality.

Facile synthesis of high-swelling cyclodextrin polymer for sustainable water purification

Porous materials are widely used in the adsorption field to sequester pollutants to address the global sustainable water security and water scarcity concerns. However, there are still challenges that limit their industrial application, especially the required rational design and construction of porous structures. Here, we report a high-swelling cyclodextrin polymer (His-CDP) that is facilely synthesized without additional design and templates, to achieve high affinity, non-specific and rapid adsorption of pollutants. His-CDP rapidly swells in water with high swelling ratio (706 %), and swelling results in a significant increase in the specific surface area (from 38 m2∙g-1 of dry state to 562 m2∙g-1 of wet state) and abundant adsorption sites. The adsorption rates of His-CDP for methylene blue (MB), bisphenol A (BPA), and copper ion (Cu2+) are 0.304 g∙mg-1∙min-1, 0.370 g∙mg-1∙min-1, and 0.117 g∙mg-1∙min-1, respectively, which are 106-571 times, 5-15 times, and 36-58 times higher than those of activated carbons and low-swelling cyclodextrin polymer. The maximum adsorption capacities of His-CDP for MB, BPA, and Cu2+ are 1.06 mol∙g-1, 0.35 mol∙g-1, and 1.95 mol∙g-1, respectively. His-CDP has high stability, good reproducibility, cost-effective regeneration, and is expected to be produced on a large scale. As a demonstration application, we demonstrate that His-CDP outperforms activated carbons in rapid, high-capacity purification of tap water, treatment of industrial wastewater and remediation of polluted surface water. Our findings open the way for the application of high-swelling polymers in sustainable water purification.

Adsorption kinetics and mechanisms of nano chitosan coated cotton fiber for the removal of heavy metals from industrial effluents

The present study successfully removed heavy metals from industrial effluent using nanochitosan-coated cotton fiber (NCCF) crosslinked with citric acid, demonstrating the potential of advanced technologies in removing heavy metals from large amounts of wastewater caused by the world's unchecked population growth and widespread industrialization that has caused pollution. Structural, morphological, and thermal properties of NCCF were determined. Results revealed that the nanochitosan component improves the adsorption capacity of cotton fiber (CF) through the increased surface area and porosity of NCCF. Sorption studies were conducted based on pH, kinetics, isotherms, and desorption results. The Langmuir and Freundlich adsorption isotherms were utilized to examine the CF and NCCF adsorption mechanisms. NCCF exhibited maximum Langmuir adsorption capacities of 4.76 mmol/g for Cd2+, 6.40 mmol/g for Pb2+, and 12.50 mmol/g for Cr6+. Kinetic studies revealed that the pseudo-first-order kinetics model best describes the adsorption process. The results of the adsorption kinetics study showed that NCCF has a shorter half-time of adsorption than CF does during the adsorption process. This suggests that NCCF has a greater initial adsorption rate and adsorption capacity than CF. These findings are expected to lead to industrial applications in wastewater treatment as sustainable and highly effective materials.

Adsorption of Au(III), Pt(IV), Pd(II), and Rh(III) ions on activated carbon in a batch reactor supported by microwave radiation

This study investigates the simultaneous recovery of noble metal ions using commercially available activated carbon (AC). Adsorption was carried out in a closed batch reactor enhanced by microwave radiation, creating high-pressure and high-temperature conditions. The effects of AC mass, process time, temperature, pH, and ionic strength of the solution were examined. High-temperature, high-pressure, and microwave radiation proved to be effective means of chemical activation, resulting in nearly 100% adsorption efficiency. It is proposed that microwave radiation significantly increases the local temperature at the surface of activated carbon, altering the adsorption mechanism. This enhancement led to higher recovery yields compared to traditional batch reactors without microwave support. The results demonstrate the significant potential of this method for efficient metal recovery.

Biomass-Derived Materials in Perovskite Solar Cells: Recent Progress and Future Prospects

As a promising photovoltaic (PV) technology, perovskite solar cells (PSCs) have made significant progress in attaining high PCE, while challenges remain regarding stability and low cost. Conventional PSCs using noble metals (e. g., Au and Ag) as back electrodes and transparent conducting oxides as front electrodes contribute significantly to their high costs. PSCs comprising biomass-derived materials, such as biocarbon as back electrodes and flexible and transparent cellulosic substrates as front electrodes, offer a promising solution to address these issues. These approaches have the potential to simultaneously improve stability and decrease manufacturing costs, making PSCs closer to commercialization. This review article furnishes a comprehensive overview of recent developments in biocarbon-based perovskite solar cells (C-PSCs), focusing on various biomass-derived biocarbon materials utilized as back electrodes in different C-PSCs device structures. This article also compiles the advancement of flexible and transparent cellulosic substrate-based PSCs by highlighting the fundamentals of PSC and C-PSC architectures, the basics of biomass, and the synthesis of biocarbon. Finally, this review discusses the current challenges and future research directions for optimizing biocarbon materials and cellulosic substrates in PSC technology.

MnFe2O4-loaded bamboo pulp carbon-based aerogel composite: synthesis, characterization and adsorption behavior study for heavy metals removal

Heavy metal wastewater is a direct threat to the ecological environment and human health because it is highly toxic at low concentrations. Therefore, it is very important to explore and develop efficient wastewater treatment agents. MnFe2O4-loaded bamboo pulp carbon-based aerogel (MCA) is prepared by directional freeze-drying and carbonization. SEM, TEM, XPS, XRD, BET and FTIR are used to evaluate the physical and chemical properties of MCA. Meanwhile, the adsorption performances of MCA on Pb2+, Cu2+ and Cd2+ are also studied by adsorption kinetics, isothermal curves and thermodynamics. The results show that the adsorption process involves chemical adsorption and physical adsorption, and the adsorption process is a spontaneous endothermic process. The maximum adsorption capacities of MCA for Pb2+, Cu2+ and Cd2+ obtained in the adsorption isotherm experiments were 74.38, 84.21 and 73.63 mg g-1, respectively, showing excellent adsorption performance for Pb2+, Cu2+ and Cd2+. Therefore, the MCA has potential application for wastewater purification of heavy metals containing Pb2+, Cu2+ and Cd2+, meanwhile, this study provides some guidance for the design and application of microspheres for the separation and removal of Pb2+, Cu2+ and Cd2+.

Carbonaceous adsorbents in wastewater treatment: From mechanism to emerging application

Adsorption is of great significance in the water pollution control. Carbonaceous adsorbents, such as carbon quantum dots, carbon nanotubes, graphene, and activated carbons, have long been deployed in sustainable wastewater treatment due to their excellent physical structure and strong interaction with various pollutants; these features allow them to spark greater interest in environmental remediation. Although numerous eye-catch researches on carbon materials in wastewater treatment, there is a lack of comprehensive comparison and summary of the vivid structure-activity-application relationships of different types of carbonaceous adsorbents at the molecular and atomic level. Herein, this review aims to scrutinize and contrast the adsorption mechanisms of carbonaceous adsorbents with different dimensions, analyzing the qualitative differences in adsorption capacity from microscopic perspectives, structural diversity caused by preparation methods, and environmental external factors affecting adsorption occurrence. Then, a quantitatively in-depth critical appraisal of traditional and emerging contaminants in wastewater treatment using carbonaceous adsorbents, and innovative strategies for enhancing their adsorption capacity are discussed. Finally, in the context of growing imposed circularity and zero waste wishes, this review offers some promising insights for carbonaceous adsorbents in achieving sustainable wastewater treatment.

Novel Nanocomposite of Carbonized Chitosan-Zinc Oxide-Magnetite for Adsorption of Toxic Elements from Aqueous Solutions

Herein, a novel nanocomposite (carbonized chitosan-zinc oxide-magnetite, CCZF) was developed to effectively remove toxic elements in water remediation. Combining the high adsorption capacities of chitosan with the magnetic properties of magnetite and the chemical stability of zinc oxide, the combination of these unique properties makes it an efficient and versatile material that offers a sustainable solution for water purification. The (CCZF) nanocomposite was synthesized through the coprecipitation method and characterized using various techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and zeta potential analysis. The results showed impressive maximum adsorption capacities of 891.34 mg/g for Ni2+, 1269.35 mg/g for Co2+, and 1502.67 mg/g for Cu2+, fitting well with a modified Langmuir isotherm model. The adsorption process was spontaneous and endothermic, characterized by low positive enthalpy (ΔH) values ranging from 10.95 to 34.9 kJ/mol, indicative of the physical adsorption mechanism. Additionally, the nanocomposite demonstrated good reusability over multiple adsorption and desorption cycles. This research highlights the potential of the (CCZF) nanocomposite as a highly efficient, reusable adsorbent for the removal of toxic elements from aqueous solutions, contributing significantly to environmental remediation efforts and pollution control.

Synergistic effect of rice husk-derived activated carbon modified by Ni/Al-layered double hydroxides for lead removal from industrial wastewater

To enhance the adsorption efficiency of activated carbon for heavy metals, herein we synthesized a novel composite adsorbent by loading of nickel/aluminum layered double hydroxides (Ni/Al-LDH) onto a chemically modified Egyptian rice husk-derived activated carbon. The characterization techniques used for determining the chemical and surface structure of the prepared composite were including FTIR, XRD, SEM, and BET which confirmed the successful loading of LDH onto the prepared activated carbon surface. The modified activated carbon established significantly upgraded performance in eliminating lead ions from wastewater. Adsorption studies revealed that the process follows Freundlich isotherm and pseudo-second-order kinetics, indicating chemisorption as the rate-determining step. The maximum lead ions removal (using 50 ppm concentration solution) was 82% after 210 min at pH 7. The improved lead ions removal efficiency was attributed to the synergistic effect of the activated carbon's surface chemistry and the LDH's ion exchange properties. The presence of chelating groups like hydroxyl (-OH), amide (-CO-NH-), carboxylate (-COOH), and nitrogen-containing functional groups on the activated carbon surface, along with the hydroxide groups of the LDH, facilitates the complexation and adsorption of lead ions.

Optimization of hydrochar synthesis conditions for enhanced Cd(II) and Pb(II) adsorption in mono and multimetallic systems

The characterisation of hydrochars derived from Sargassum biomass collected along the Mexican Caribbean coast reveals their favourable morphology and chemical composition for incorporating metal ions, including Cd(II) and Pb(II). Among the synthesized materials, HCS-3, produced at 180 °C with a 2 h residence time, exhibited superior yield, specific area, carbon content, and capacity for removing Cd(II) and Pb(II). Adsorption equilibrium studies demonstrate the presence of adsorption processes during Cd(II) and Pb(II) retention on HCS-3, with adsorption capacities slightly exceeding 140 and 340 mg g⁻1, respectively. Notably, HCS-3 shows a greater affinity for Pb(II) over Cd(II) when both elements are present concurrently. The physicochemical analysis through FTIR spectroscopy, functional group analysis, point of zero charge determination, SEM/EDS, and other techniques evidenced that HCS-3 possesses favourable characteristics to serve as a heavy metal adsorbent. These findings underscore the efficacy of hydrochars from Sargassum biomass in removing heavy metals, suggesting their potential as superior adsorbents compared to traditional or novel materials, and advising its possible versatility for other pollutants. Utilizing these hydrochars could mitigate the economic and environmental impact of Sargassum biomass by repurposing it for valuable applications.

Revolutionizing dairy waste: emerging solutions in conjunction with microbial engineering

The dairy industry is grappling with significant challenges in managing effluent due to environmental concerns and stringent regulatory demands, necessitating innovative solutions. The paper investigates how microbial engineering is transforming the treatment of dairy wastewater, offering advanced methods to minimize environmental impact and enhance sustainability. It delves into the current challenges faced by the dairy industry, such as regulatory compliance and the limitations of traditional treatment technologies, and introduces microbial engineering as a promising solution for effluent management. Microbial engineering leverages genetic engineering techniques and microorganisms to enhance the efficiency of treatment processes like bioaugmentation and bioremediation. The environmental and economic benefits of microbial engineering, highlighting its potential to reduce pollution and lower operational costs for the dairy industry. The specific figures can vary based on factors like farm size and location, studies suggest that microbial engineering can reduce wastewater pollution by up to 50% and nutrient runoff by 30%. It also identifies key challenges and there are still areas including strains for specific pollutants (drugs, hormones), enhance degradation pathways, and increase microbes' stability (stress tolerance, long-term viability) that require further innovation to maximize its benefits. Through case studies and success stories, the paper demonstrates practical applications of microbial engineering in managing dairy effluent, illustrating how it can revolutionize industrial practices for a more sustainable future.

Comparison of biocrude production and characterization from Persian Gulf Sargassum angustifolium macroalgae, Chlorella vulgaris, and Spirulina sp. microalgae using hydrothermal liquefaction (HTL): Potential of solid residue for heavy metal adsorption

Biocrude production using the hydrothermal liquefaction (HTL) process is a promising alternative energy source to conventional fossil fuels. Using algal feedstock types in this process has many advantages, such as not needing to dry a high moisture content, which consumes much energy. In this study, the feedstock types of Sargassum angustifolium macroalgae, Chlorella vulgaris, and Spirulina sp. microalgae affected the yield and property of the biocrude products were obtained at 350 °C, 18 MPa, 35 min residence time, and 8.7 wt% feedstock concentration. The biocrude yields from Sargassum angustifolium, Chlorella vulgaris, and Spirulina sp. were 26.15 wt%, 55.8 wt%, and 56.32 wt%, respectively. These values revealed that feedstock's carbon and nitrogen contents have the most effect on the biocrude yield, and increasing these elements increases the biocrude yields. Moreover, the properties of the produced biocrudes revealed that the main components were esters, organic acids, ketones, aldehydes, aromatic rings, amides, amines, alcohol, and phenol. The thermal gravimetric analysis (TGA) results of biocrudes showed the decomposition of more organic components at the 175-600 °C temperature range. Also, the simulated distillation of biocrudes showed that most biocrude components from Sargassum angustifolium and Chlorella vulgaris are the same as heavy naphtha, and the biocrude from Spirulina sp. is similar to kerosene. These results showed that the produced biocrude from Chlorella vulgaris has a higher yield and quality than other resources. The quality of the biocrude produced from Sargassum angustifolium is comparable to other biocrudes. Besides, the higher solid-phase yield produced from Sargassum angustifolium was used as a heavy metal biosorbent. The effect of adsorbent concentration and adsorption time on adsorption efficiency was investigated. Results showed that the maximum adsorption efficiency of Fe2+, Zn2+, and Mn2+ was 47.07 wt%, 48.93 wt%, and 42.47 wt%, respectively, at 2 g/L adsorbent concentration and 60 min adsorption time, and the structure destruction of the solid phase was carried out under the biosorption process.

Recent and sustainable advances in phytoremediation of heavy metals from wastewater using aquatic plant species: Green approach

A key component in a nation's economic progress is industrialization, however, hazardous heavy metals that are detrimental to living things are typically present in the wastewater produced from various industries. Therefore, before wastewater is released into the environment, it must be treated to reduce the concentrations of the various heavy metals to maximum acceptable levels. Even though several biological, physical, and chemical remediation techniques are found to be efficient for the removal of heavy metals from wastewater, these techniques are costly and create more toxic secondary pollutants. However, phytoremediation is inexpensive, environmentally friendly, and simple to be applied as a green technology for heavy metal detoxification in wastewater. The present study provides a thorough comprehensive review of the mechanisms of phytoremediation, with an emphasis on the possible utilization of plant species for the treatment of wastewater containing heavy metals. We have discussed the concept, its applications, advantages, challenges, and independent variables that determine how successful and efficient phytoremediation could be in the decontamination of heavy metals from wastewater. Additionally, we argue that the standards for choosing aquatic plant species for target heavy metal removal ought to be taken into account, as they influence various aspects of phytoremediation efficiency. Following the comprehensive and critical analysis of relevant literature, aquatic plant species are promising for sustainable remediation of heavy metals. However, several knowledge gaps identified from the review need to be taken into consideration and possibly addressed. Therefore, the review provides perspectives that indicate research needs and future directions on the application of plant species in heavy metal remediation.

Pore Engineering in Biomass-Derived Carbon Materials for Enhanced Energy, Catalysis, and Environmental Applications

Biomass-derived carbon materials (BDCs) are highly regarded for their renewability, environmental friendliness, and broad potential for application. A significant advantage of these materials lies in the high degree of customization of their physical and chemical properties, especially in terms of pore structure. Pore engineering is a key strategy to enhance the performance of BDCs in critical areas, such as energy storage, catalysis, and environmental remediation. This review focuses on pore engineering, exploring the definition, classification, and adjustment techniques of pore structures, as well as how these factors affect the application performance of BDCs in energy, catalysis, and environmental remediation. Our aim is to provide a solid theoretical foundation and practical guidance for the pore engineering of BDCs to facilitate the rapid transition of these materials from the laboratory to industrial applications.

Aqueous and Colloidal Dynamics in Size-Fractionated Paddy Soil Aggregates with Multiple Metal Contaminants under Redox Alternations

Soil contamination by multiple metals is a significant concern due to the interlinked mobilization processes. The challenges in comprehending this issue arise from the poorly characterized interaction among different metals and the complexities introduced by spatial and temporal heterogeneity in soil systems. We delved into these complexities by incubating size-fractionated paddy soils under both anaerobic and aerobic conditions, utilizing a combination of techniques for aqueous and colloidal analysis. The contaminated paddy soil predominantly consisted of particles measuring <53, 250-53, and 2000-250 μm, with the <53 μm fractions exhibiting the highest concentrations of multiple metals. Interestingly, despite their higher overall content, the <53 μm fractions released less dissolved metal. Furthermore, glucose enhanced the release of arsenic while simultaneously promoting the sequestration of other metals, such as Pb, Zn, and Cu. Utilizing asymmetric flow field-flow fractionation, we unveiled the presence of both fine (0.3-130 kDa) and large (130-450 nm) colloidal pools, each carrying various metals with different affinities for iron minerals and organic matter. Our results highlighted the pivotal role of the <53 μm fraction as a significant reservoir for multiple metal contaminants in paddy soils, in which the colloidal metals were mainly associated with organic matter. These findings illuminated the size-resolved dynamics of soil metal cycling and provided insights for developing remediation strategies for metal-contaminated soil ecosystems.

The molecular insights of cyanobacterial bioremediations of heavy metals: the current and the future challenges

In recent years, overexplorations of ore and the growth of industries are the prime factors in the release of heavy metals in environments. As a result, the food crops and water bodies are contaminated with metals which may have several adverse effects on the health of humans and other living species. These metals and metalloids, such as Zn, Cu, Mn, Ni, Cr, Pb, Cd, and As, upset the biochemical pathways of metabolite synthesis in living organisms and contribute to the etiology of different diseases. Microorganisms include bacteria, archaea, viruses, and many unicellular eukaryotes, which can span three domains of life-Archaea, Bacteria, and Eukarya-and some microorganisms, such as cyanobacteria, have shown high efficiency in the biosorption rate of heavy metals. Cyanobacteria are suitable for bioremediation as they can grow in adverse environments, have a less negative impact on the surrounding environment, and are relatively cheaper to manage. The structure of cyanobacteria has shown no extensive internal-bound membranes, so it can directly employ the physiological mechanisms to uptake heavy metals from contamination sites. Such biochemical makeups are suitable for managing and bioremediating heavy metal concentrations in polluted environments. This review aims to explore the potential of cyanobacteria in the bioremediation of heavy metals and metalloids in water bodies. Additionally, we have identified the prospects for enhancing bioremediation effectiveness.

Agricultural biomass/waste-based materials could be a potential adsorption-type remediation contributor to environmental pollution induced by pesticides-A critical review

The widespread use of pesticides that are inevitable to keep the production of food grains brings serious environmental pollution problems. Turning agricultural biomass/wastes into materials addressing the issues of pesticide contaminants is a feasible strategy to realize the reuse of wastes. Several works summarized the current applications of agricultural biomass/waste materials in the remediation of environmental pollutants. However, few studies systematically take the pesticides as an unitary target pollutant. This critical review comprehensively described the remediation effects of crop-derived waste (cereal crops, cash crops) and animal-derived waste materials on pesticide pollution. Adsorption is considered a superior and highlighted effect between pesticides and materials. The review generalized the sources, preparation, characterization, condition optimization, removal efficiency and influencing factors analysis of agricultural biomass/waste materials. Our work mainly emphasized the promising results in lab experiments, which helps to clarify the current application status of these materials in the field of pesticide remediation. In the meantime, rigorous pros and cons of the materials guide to understand the research trends more comprehensively. Overall, we hope to achieve a large-scale use of agricultural biomass/wastes.

Recent advances in applications of animal biowaste-based activated carbon as biosorbents of water pollutants: a mini-review

Advances in green engineering and technology have revealed a number of environmentally acceptable alternatives for water purification. In line with this, recent advances in biosorption of pollutants from aqueous solutions using animal biowaste-based activated carbon (AC) are reported herein. Apart from the fish scale-derived AC which is extensively documented, animal bones, among the rest others, have been studied most widely, followed by hair and feathers. Out of the various target water pollutants, removal of heavy metals has been mostly studied. Majority of the reports showed the Freundlich isotherm and pseudo second order as the best fit. Few investigations on the thermodynamics of the adsorption studies and reports on the Gibbs free energy change (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) have also been discussed in this report. It has been concluded that while plant-based AC has gained wide interest, the same is not true for the animal-based counterpart albeit the latter's potential for high sorption efficiency as seen in the present report.

Waste for Product-Synthesis and Electrocatalytic Properties of Palladium Nanopyramid Layer Enriched with PtNPs

The presented research is the seed of a vision for the development of a waste-for-product strategy. Following this concept, various synthetic solutions containing low concentrations of platinum group metals were used to model their recovery and to produce catalysts. This is also the first report that shows the method for synthesis of a pyramid-like structure deposited on activated carbon composed of Pd and Pt. This unique structure was obtained from a mixture of highly diluted aqueous solutions containing both metals and chloride ions. The presence of functional groups on the carbon surface and experimental conditions allowed for: the adsorption of metal complexes, their reduction to metal atoms and enabled further hierarchical growth of the metal layer on the carbon surface. During experiments, spherical palladium and platinum nanoparticles were obtained. The addition of chloride ions to the solution promoted the hierarchical growth and formation of palladium nanopyramids, which were enriched with platinum nanoparticles. The obtained materials were characterized using UV-Vis, Raman, IR spectroscopy, TGA, SEM/EDS, and XRD techniques. Moreover, Pd@ROY, Pt@ROY, and Pd-Pt@ROY were tested as possible electrocatalysts for hydrogen evolution reactions.

Mitigating pb toxicity in Sesbania sesban L. through activated charcoal supplementation: a hydroponic study on enhanced phytoremediation

BACKGROUND

Soil contamination by heavy metals is a critical environmental challenge, with Pb being of particular concern due to its propensity to be readily absorbed and accumulated by plants, despite its lack of essential biological functions or beneficial roles in cellular metabolism. Within the scope of phytoremediation, the use of plants for the decontamination of various environmental matrices, the present study investigated the potential of activated charcoal (AC) to enhance the tolerance and mitigation capacity of S. sesban seedlings when exposed to Pb. The experiment was conducted as a factorial arrangement in a completely randomized design in hydroponic conditions. The S. sesban seedlings were subjected to a gradient of Pb concentrations (0, 0.02, 0.2, 2, and 10 mg/L) within the nutrient solution, alongside two distinct AC treatments (0 and 1% inclusion in the culture media). The study reached its conclusion after 60 days.

RESULTS

The seedlings exposed to Pb without AC supplementation indicated an escalation in peroxidase (POX) activity, reactive oxygen species (ROS), and malondialdehyde (MDA) levels, signaling an increase in oxidative stress. Conversely, the incorporation of AC into the treatment regime markedly bolstered the antioxidative defense system, as evidenced by the significant elevation in antioxidant capacity and a concomitant reduction in the biomarkers of oxidative stress (POX, ROS, and MDA).

CONCLUSIONS

With AC application, a notable improvement was observed in the chlorophyll a, total chlorophyll, and plant fresh and dry biomass. These findings illuminate the role of activated charcoal as a viable adjunct in phytoremediation strategies aimed at ameliorating heavy metal stress in plants.

Insights into Activation Pathways of Recovered Carbon Black (rCB) from End-of-Life Tires (ELTs) by Potassium-Containing Agents

This study explores the conversion of recovered carbon black (rCB) from end-of-life tires (ELTs) into activated carbons (ACs) using potassium-based activators, targeting enhanced textural properties development. The research focuses on the interaction between potassium and rCB, with the aim of understanding the underlying mechanisms of rCB activation. The study investigates several parameters of KOH activation, including the KOH/rCB mass ratio (1:3 to 1:6), activation temperatures (700-900 °C), activation time (1-4 h), and heating rate (5-13 °C/min). It also assesses the effects of different potassium salts (KCl, K2CO3, CH3COOK, and K2C2O4) on porosity and surface characteristics of the rCB/ACs. Furthermore, the role of the physical state of KOH as an activator (solid and gas-solid) was examined, alongside a comparative analysis with NaOH to evaluate the distinct effects of potassium and sodium ions. Optimal conditions were identified at an 800 °C activation temperature, a 7 °C/min heating rate, a 1:5 KOH/rCB ratio, and a 4 h activation period. X-ray diffraction analysis showed the formation of several K-phases, such as K2CO3, K2CO3·1.5H2O, K4(CO3)2·(H2O)3, KHCO3, and K2O. The effectiveness of the potassium salts was ranked as follows: KOH > K2C2O4 > CH3COOK > K2CO3 > KCl, with KOH emerging as the most effective. Notably, the gas-solid reaction of KOH/rCB was indicated as a contributor to the activation process. Additionally, it was concluded that the role of KOH in enhancing the textural properties of rCB was primarily due to the interaction of K+ ions with the graphite-like structure of rCB, compared to the effects observed with NaOH. This research introduces novel insights into the specific roles of different potassium salts and KOH activation conditions in optimizing the textural characteristics of rCB/ACs.

Equilibrium and Kinetic Studies on Adsorption of Neutral and Ionic Species of Organic Adsorbates from Aqueous Solutions on Activated Carbon

This work presents comprehensive studies of the adsorption of neutral and ionic forms of organic adsorbates from aqueous solutions on activated carbon. The influence of pH on the equilibrium and kinetics of the adsorption of methylene blue (MB) and organic acids, benzoic (BA), 2-nitrobenzoic (2-NBA), 3-nitrobenzoic (3-NBA), and 4-nitrobenzoic (4-NBA) acid, was investigated. Experimental adsorption isotherms were analyzed using the generalized Langmuir isotherm equation (R2 = 0.932-0.995). Adsorption rate data were studied using multiple adsorption kinetics equations, of which the multi-exponential equation gave the best fit quality (R2 - 1 = (6.3 × 10-6)-(2.1 × 10-3)). The half-time was also used to represent the effect of pH on adsorption kinetics. Strong dependences of the adsorption efficiency on the solution pH were demonstrated. In the case of organic acid adsorption, the amount and rate of this process increased with a decrease in pH. Moreover, larger adsorbed amounts of methylene blue were recorded in an alkaline environment in a relatively short time. The maximum absorbed amounts were 11.59 mmol/g, 6.57 mmol/g, 9.38 mmol/g, 2.70 mmol/g, and 0.24 mmol/g for BA, 2NBA, 3-NBA, 4-NBA, and MB. The pure activated carbon and the selected samples after adsorption were investigated using thermal analysis and X-ray photoelectron spectroscopy.

Insights into the biogeochemical transformation, environmental impacts and biochar-based soil decontamination of antimony

Every year, a significant amount of antimony (Sb) enters the environment from natural and anthropogenic sources like mining, smelting, industrial operations, ore processing, vehicle emissions, shooting activities, and coal power plants. Humans, plants, animals, and aquatic life are heavily exposed to hazardous Sb or antimonide by either direct consumption or indirect exposure to Sb in the environment. This review summarizes the current knowledge about Sb global occurrence, its fate, distribution, speciation, associated health hazards, and advanced biochar composites studies used for the remediation of soil contaminated with Sb to lessen Sb bioavailability and toxicity in soil. Anionic metal(loid) like Sb in the soil is significantly immobilized by pristine biochar and its composites, reducing their bioavailability. However, a comprehensive review of the impacts of biochar-based composites on soil Sb remediation is needed. Therefore, the current review focuses on (1) the fundamental aspects of Sb global occurrence, global soil Sb contamination, its transformation in soil, and associated health hazards, (2) the role of different biochar-based composites in the immobilization of Sb from soil to increase biochar applicability toward Sb decontamination. The review aids in developing advanced, efficient, and effective engineered biochar composites for Sb remediation by evaluating novel materials and techniques and through sustainable management of Sb-contaminated soil, ultimately reducing its environmental and health risks.

Equilibrium, Kinetic, and Diffusion Mechanism of lead(II) and cadmium(II) Adsorption onto Commercial Activated Carbons

The adsorption of Pb(II) and Cd(II) on three commercial microporous activated carbons was analysed. Adsorption kinetics and statistics were investigated, and the results were described with different models. The highest values of the correlation coefficient R2 were obtained for the pseudo-second-order kinetics model for all ions tested and all sorbents used. The adsorption process was found to be determined by both diffusion in the liquid layer and intraparticle diffusion. The adsorption equilibrium is very well described by Langmuir, Temkin, Thoth or Jovanovic isotherm models. Based on the values of n from the Freundlich isotherm and KL from the Langmuir isotherm, the adsorption of cadmium and lead ions was found to be favourable. The highest monolayer capacities were obtained during the adsorption of lead ions (162.19 mg/g) and for cadmium (126.34 mg/g) for activated carbon WG-12. This carbon is characterised by the highest amount of acid functional groups and the largest specific surface area. The adsorption efficiency of the tested ions from natural water is lower than that from a model solution made from deionised water. The lowest efficiencies are obtained when the process occurs from highly mineralised water.

The Application of Metal-Organic Frameworks in Water Treatment and Their Large-Scale Preparation: A Review

Over the last few decades, there has been a growing discourse surrounding environmental and health issues stemming from drinking water and the discharge of effluents into the environment. The rapid advancement of various sewage treatment methodologies has prompted a thorough exploration of promising materials to capitalize on their benefits. Metal-organic frameworks (MOFs), as porous materials, have garnered considerable attention from researchers in recent years. These materials boast exceptional properties: unparalleled porosity, expansive specific surface areas, unique electronic characteristics including semi-conductivity, and a versatile affinity for organic molecules. These attributes have fueled a spike in research activity. This paper reviews the current MOF-based wastewater removal technologies, including separation, catalysis, and related pollutant monitoring methods, and briefly introduces the basic mechanism of some methods. The scale production problems faced by MOF in water treatment applications are evaluated, and two pioneering methods for MOF mass production are highlighted. In closing, we propose targeted recommendations and future perspectives to navigate the challenges of MOF implementation in water purification, enhancing the efficiency of material synthesis for environmental stewardship.

Synthesis of surface-modified porous polysulfides from soybean oil by inverse vulcanization and its sorption behavior for Pb(II), Cu(II), and Cr(III)

Guided by efficient utilization of natural plant oil and sulfur as low-cost sorbents, it is desired to tailor the porosity and composition of polysulfides to achieve their optimal applications in the management of aquatic heavy metal pollution. In this study, polysulfides derived from soybean oil and sulfur (PSSs) with improved porosity (10.2-22.9 m2/g) and surface oxygen content (3.1-7.0 wt.%) were prepared with respect to reaction time of 60 min, reaction temperature of 170 °C, and mass ratios of sulfur/soybean oil/NaCl/sodium citrate of 1:1:3:2. The sorption behaviors of PSSs under various hydrochemical conditions such as contact time, pH, ionic strength, coexisting cations and anions, temperature were systematically investigated. PSSs presented a fast sorption kinetic (5.0 h) and obviously improved maximum sorption capacities for Pb(II) (180.5 mg/g), Cu(II) (49.4 mg/g), and Cr(III) (37.0 mg/g) at pH 5.0 and T 298 K, in comparison with polymers made without NaCl/sodium citrate. This study provided a valuable reference for the facile preparation of functional polysulfides as well as a meaningful option for the removal of aquatic heavy metals.

Uniformly dispersed ruthenium nanoparticles on porous carbon from coffee waste outperform platinum for hydrogen evolution reaction in alkaline media

Biowaste-derived carbon materials are a sustainable, environmentally friendly, and cost-effective way to create valuable materials. Activated carbon can be a supporting material for electrocatalysts because of its large specific surface area and porosity. However, activated carbon has low catalytic activity and needs to be functionalized with heteroatoms, metals, and combinations to improve conductivity and catalytic activity. Ruthenium (Ru) catalysts have great potential to replace bench market catalysts in hydrogen evolution reaction (HER) applications due to their similar hydrogen bond strength and relatively lower price. This study reports on the synthesis and characterizations of carbon-supported Ru catalysts with large surface areas (~ 1171 m2 g-1) derived from coffee waste. The uniformly dispersed Ru nanoparticles on the porous carbon has excellent electrocatalytic activity and outperformed the commercial catalyst platinum on carbon (Pt/C) toward the HER. As-synthesized catalyst needed only 27 mV to reach a current density of 10 mA cm-2, 58.4 mV dec-1 Tafel slope, and excellent long-term stability. Considering these results, the Ru nanoparticles on coffee waste-derived porous carbon can be utilized as excellent material that can replace platinum-based catalysts for the HER and contribute to the development of eco-friendly and low-cost electrocatalyst materials.

Inverse vulcanization induced oxygen modified porous polysulfides for efficient sorption of heavy metals

The applications of polysulfides derived from natural plant oil and sulfur via the inverse vulcanization in the removal of heavy metals from aqueous solutions suffered from their low porosity and scarce surface functionality because of their hydrophobic surfaces and bulk characteristics. In this study, polysulfides from sulfur and palm oil (PSPs) with significantly enhanced porosity (13.7-24.1 m2/g) and surface oxygen-containing functional groups (6.9-8.6 wt.%) were synthesized with the optimization of process conditions including reaction time, temperature, and mass ratios of sulfur/palm oil/NaCl/sodium citrate. PSPs were applied as sorbents to remove heavy metals present in aqueous solutions. The integration of porosity and oxygen modification allowed a fast kinetic (4.0 h) and enhanced maximum sorption capacities for Pb(II) (218.5 mg/g), Cu(II) (74.8 mg/g), and Cr(III) (68.4 mg/g) at pH 5.0 and T 298 K comparing with polysulfides made without NaCl/sodium citrate. The sorption behaviors of Pb(II), Cu(II), and Cr(III) on PSPs were highly dependent on the solution pH values and ionic strength. The sorption presented excellent anti-interference capability for the coexisting cations and anions. The sorption processes were endothermic and spontaneous. This work would guide the preparation of porous polysulfides with surface modification as efficient sorbents to remediate heavy metals from aqueous solutions.

Photocatalytic degradation of organic dyes using reduced graphene oxide (rGO)

Photocatalysts have developed into a successful strategy for degrading synthetic and organic toxins, such as chemicals and dyes, in wastewater. In this study, graphene oxide was reduced at different temperatures and used for degrading indigo carmine and neutral red dyes. The wide surface areas, strong adsorption sites, and oxygen functionalities of reduced graphene oxide (rGO) at 250 °C (rGO-250) produced more photocatalytic degradation efficiency and adsorption percentage. The catalyst dosage, initial dye concentration, solution pH and recyclability were all used to optimize the photocatalytic activity of rGO-250. This research presents a capable nano-adsorbent photocatalyst for the efficient degradation of organic dyes. GO and rGOs were also investigated for carbon dioxide (CO2) absorption properties. Results showed that rGO-250 has better CO2 adsorption properties than other rGOs. Overall, it was observed that rGO-250 has better photocatalytic and CO2 adsorption capabilities compared to graphene oxide reduced at different temperatures.

Adsorption of Organic Pollutants on Carbonaceous Adsorbents Prepared by Direct Activation of Sweet Cherry Stones

The main objective of this study was to assess the usefulness of the sweet cherry stones for the production of carbonaceous adsorbents by means of direct physical activation method, using conventional and microwave variant of heating. The adsorbents were characterized in terms of textural parameters, acidic-basic character of the surface, electrokinetic properties and their suitability for drinking water purification. Adsorption tests were carried out against three organic compounds - Triton X-100 (surfactant), bovine serum albumin (protein) and methylene blue (synthetic dye). Depending on the variant of heating applied during activation procedure, the obtained activated biochars differed significantly in terms of the elemental composition, acidic-basic properties as well as degree of specific surface development and the type of porous structure generated. Adsorption tests have showed that the efficiency of organic pollutants removal from aqueous solutions depends significantly not only on the type of the adsorbent and adsorbate applied, but also on the temperature and pH of the system. The sample prepared by microwave-assisted direct activation proved to be very effective in terms of all tested organic pollutants adsorption. The maximum sorption capacity toward Triton X-100, bovine serum albumin and methylene blue reached the level of 86.5, 23.4 and 81.1 mg/g, respectively.

Synthesis and characterization of iron oxide-commercial activated carbon nanocomposite for removal of hexavalent chromium (Cr6+) ions and Mordant Violet 40 (MV40) dye

Iron Oxide-commercial activated carbon nanocomposite (CAC-IO) was prepared from commercial activated carbon (CAC) by the co-precipitation method, and the resulting nanocomposite was used as an adsorbent to remove hexavalent chromium (Cr6+) ions and Mordant Violet 40 (MV40) dye from wastewater. The produced materials (CAC, CAC after oxidation, and CAC-IO) were comparatively characterized using FTIR, BET, SEM, EDX TEM, VSM, and XRD techniques. The adsorption mechanism of Cr6+ ions and MV40 dye on CAC-IO was examined using Langmuir and Freundlich isotherm models.. Different models were applied to know the adsorption mechanism and it was obtained that Pseudo-second order fits the experimental data better. This means that the adsorption of the adsorbate on the nanocomposite was chemisorption. The maximum removal percent of Cr6+ ions by CAC-IO nanocomposite was 98.6% determined as 2 g L-1 adsorbent concentration, 100 mg L-1 initial pollutant concentration, solution pH = 1.6, the contact time was 3 h and the temperature was room temperature. The maximum removal percentage of Mordant Violet 40 dye (C.I. 14,745) from its solutions by CAC-IO nanocomposite was 99.92% in 100 mg L-1 of initial dye concentrations, 1.0 g L-1 of adsorbent concentration, solution pH = 2.07, the contact time was 3 h. The MV40 dye adsorption on CAC-IO was the most fitted to the Freundlich isotherm model. The maximum adsorption capacity was calculated according to the Langmuir model as 833.3 mg g-1 at 2 g L-1 of adsorbent concentration and 400 mg L-1 of initial MV40 dye concentration. The Cr6+ ions adsorption on CAC-IO was more fitted to the Freundlich model with Qmax, equal to 312.50 mg g-1 at 1 g L-1 adsorbent concentration and 400 mg L-1 of Cr6+ ions initial concentrations.

Mesoporous Materials for Metal-Laden Wastewater Treatment

Rapid technological, industrial and agricultural development has resulted in the release of large volumes of pollutants, including metal ions, into the environment. Heavy metals have become of great concern due to their toxicity, persistence, and adverse effects caused to the environment and population. In this regard, municipal and industrial effluents should be thoroughly treated before being discharged into natural water or used for irrigation. The physical, chemical, and biological techniques applied for wastewater treatment adsorption have a special place in enabling effective pollutant removal. Currently, plenty of adsorbents of different origins are applied for the treatment of metal-containing aqueous solution and wastewater. The present review is focused on mesoporous materials. In particular, the recent achievements in mesoporous materials' synthesis and application in wastewater treatment are discussed. The mechanisms of metal adsorption onto mesoporous materials are highlighted and examples of their multiple uses for metal removal are presented. The information contained in the review can be used by researchers and environmental engineers involved in the development of new adsorbents and the improvement of wastewater treatment technologies.

Recent progress in high-performance environmental impacts of the removal of radionuclides from wastewater based on metal-organic frameworks: a review

The nuclear industry is rapidly developing and the effective management of nuclear waste and monitoring the nuclear fuel cycle are crucial. The presence of various radionuclides such as uranium (U), europium (Eu), technetium (Tc), iodine (I), thorium (Th), cesium (Cs), and strontium (Sr) in the environment is a major concern, and the development of materials with high adsorption capacity and selectivity is essential for their effective removal. Metal-organic frameworks (MOFs) have recently emerged as promising materials for removing radioactive elements from water resources due to their unique properties such as tunable pore size, high surface area, and chemical structure. This review provides an extensive analysis of the potential of MOFs as adsorbents for purifying various radionuclides rather than using different techniques such as precipitation, filtration, ion exchange, electrolysis, solvent extraction, and flotation. This review discusses various MOF fabrication methods, focusing on minimizing environmental impacts when using organic solvents and solvent-free methods, and covers the mechanism of MOF adsorption towards radionuclides, including macroscopic and microscopic views. It also examines the effectiveness of MOFs in removing radionuclides from wastewater, their behavior on exposure to high radiation, and their renewability and reusability. We conclude by emphasizing the need for further research to optimize the performance of MOFs and expand their use in real-world applications. Overall, this review provides valuable insights into the potential of MOFs as efficient and durable materials for removing radioactive elements from water resources, addressing a critical issue in the nuclear industry.

Green synthesized silver nanoparticles for iron and manganese ion removal from aqueous solutions

Microalgae and Cyanobacteria extracts can be used for the synthesis of spherical silver nanoparticles by the reduction of AgNO₃ under air atmosphere at room temperature. Here, we synthesized AgNPs using extracts of one cyanobacterium (Synechococcus elongatus) and two microalgae (Stigeoclonium sp. and Cosmarium punctulatum). The nature of the AgNPs was characterized by TEM, HR-TEM, EDS, and UV-Vis. Considering the large quantity of functional groups in the ligands of AgNPs, we suppose they could retain ion metals, which would be useful for water decontamination. Thus, their capacity to adsorb iron and manganese at concentrations of 1.0, 5.0, and 10.0 mg L^-1 in aqueous solutions was evaluated. All experiments were performed in triplicate of microorganism extract with no addition of AgNO₃ (control) and AgNP colloid (treatment) at room temperature. The ICP analyses showed that the treatments containing nanoparticles were commonly more efficient at removing Fe³⁺ and Mn²⁺ ions than the corresponding controls. Interestingly, the smaller nanoparticles (synthesized by Synechococcus elongatus) were the most effective at removing Fe³⁺ and Mn²⁺ ions, probably due to their higher surface area:volume ratio. The green synthesized AgNPs proved to be an interesting system for the manufacture of biofilters that could be used to capture contaminant metals in water.

Activated Carbon and Clay Pellets Coated with Hydroxyapatite for Heavy Metal Removal: Characterization, Adsorption, and Regeneration

In the present work, activated-carbon-containing pellets were preparedby direct chemical activation of sawdust, using clays as a binder. The obtained pellets (ACC) were coated with hydroxyapatite (HAp) nanoparticles (ACC-HAp) to improve adsorption towards Pb(II), Cu(II), Zn(II), and Ni(II). The pellets were characterized by scanning electron microscopy (SEM), by Fourier transform infrared spectroscopy (FTIR), and with a gas sorptometer. The effect of pH, contact time, and initial concentration on adsorption performance was investigated. Additionally, desorption studies were performed, and the regeneration influence on compressive strength and repeated Pb(II) adsorption was investigated. The results showed that, after coating ACC pellets with HAp nanoparticles, the adsorption capacity increased for all applied heavy metal ions. Pb(II) was adsorbed the most, and the best results were achieved at pH 6. The adsorption process followed the pseudo-second-order kinetic model. The adsorption isotherm of Pb(II) is better fitted to the Langmuir model, showing the maximum adsorption capacity of 56 and 47 mg/g by ACC-HAp and ACC pellets, respectively. The desorption efficiency of Pb(II)-loaded ACC-HAp pellets increased by lowering the pH of the acid, resulting in the dissolution of the HAp coating. The best desorption results were achieved with HCl at pH 1 and 1.5. Therefore, the regeneration procedure consisted of desorption, rinsing with distilled water, and re-coating with HAp nanoparticles. After the regeneration process, the Pb(II) adsorption was not affected. However, the desorption stage within the regeneration process decreased the compressive strength of the pellets.

Removal of heavy metals from binary and multicomponent adsorption systems using various adsorbents - a systematic review

The ecosystem and human health are both significantly affected by the occurrence of potentially harmful heavy metals in the aquatic environment. In general, wastewater comprises an array of heavy metals, and the existence of other competing heavy metal ions might affect the adsorptive elimination of one heavy metal ion. Therefore, to fully comprehend the adsorbent's efficiency and practical applications, the abatement of heavy metals in multicomponent systems is important. In the current study, the multicomponent adsorption of heavy metals from different complex mixtures, such as binary, ternary, quaternary, and quinary solutions, utilizing various adsorbents are reviewed in detail. According to the systematic review, the adsorbents made from locally and naturally occurring materials, such as biomass, feedstocks, and industrial and agricultural waste, are effective and promising in removing heavy metals from complex water systems. The systematic study further discovered that numerous studies evaluate the adsorption characteristics of an adsorbent in a multicomponent system using various important independent adsorption parameters. These independent adsorption parameters include reaction time, solution pH, agitation speed, adsorbent dosage, initial metal ion concentration, ionic strength as well as reaction temperature, which were found to significantly affect the multicomponent sorption of heavy metals. Furthermore, through the application of the multicomponent adsorption isotherms, the competitive heavy metals sorption mechanisms were identified and characterized by three primary kinds of interactive effects including synergism, antagonism, and non-interaction. Despite the enormous amount of research and extensive data on the capability of different adsorbents, several significant drawbacks hinder adsorbents from being used practically and economically to remove heavy metal ions from multicomponent systems. As a result, the current systematic review provides insights and perspectives for further studies through the thorough and reliable analysis of the relevant literature on heavy metals removal from multicomponent systems.